Role of Methadone in Induction and/or Exacerbation of Cluster Headache in Patients Treated for Opioid Addiction.

Methadone is a potent opioid agonist widely used in opioid maintenance therapy. In some countries, methadone is available for pain treatment. We report the cases of two patients with history of substance abuse (mainly heroin), who presented with cluster headache possibly related to high-dose methadone. One possible explanation for the severe pain described in these cases is hyperalgesia induced by high doses of methadone.